docs(file-storage): explain local write failures

[rafaself]

PR Checklist

• The commit message follows our guidelines: https://github.com/nestjs/docs.nestjs.com/blob/master/CONTRIBUTING.md

PR Type

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Docs
• Other... Please describe:

What is the current behavior?

The file-storage tutorial describes atomic writes but does not explain the LocalDisk zero-progress and persisted-size checks added by nestjs/storage#19.

What is the new behavior?

Add a short paragraph beside the put() explanation documenting temporary-file cleanup, preservation of an existing file on a failed filesystem write, and direct StorageError failures when writing makes no progress or the persisted size differs from the bytes written.

All existing examples and other content remain unchanged.

Does this PR introduce a breaking change?

• Yes
• No

Other information

Dependency: nestjs/storage#19 is still open. Keep this PR in draft until the corresponding implementation has landed and the documentation can describe the available behavior.

This follows the documentation recommendation in nestjs/storage#19 (review).

Validation with Node 22.23.3:

• npm run build passes, including documentation and LLM-file generation.
• npm test -- --watch=false: 58 tests pass.
• Verified the generated HTML contains the complete note once as a single paragraph, and source comparison confirms only the intended note changed.
• git diff --check passes.
• npm run lint reports 30 existing errors in unchanged TypeScript files.

The initial npm ci attempt reported missing chokidar@3.6.0 and glob-parent@5.1.2 lockfile entries. Dependencies were installed with npm install --package-lock=false; no dependency files are changed.